1. Field of the Invention
The present invention relates to an interface adapter for providing single-sided electrical contact to a circuit card bearing contact elements on two sides.
2. State of the Art
Modern personal computers are designed to be easily upgraded by swapping out old components and replacing them with newer, faster, and higher capacity parts. For example, computer memory such as dynamic random access memory (DRAM) is upgraded by inserting single in-line memory modules (SIMMs) into preexisting sockets on a motherboard. SIMMs are small circuit cards with memory chips attached and a single-sided edge connector having a data width of 32-bits. Dual in-line memory modules (DIMMs) provide greater data widths (64- and 72-bits) and higher memory density, particularly useful for size-limited applications such as notebook computers. Microprocessors are also trending toward greater data (word) widths. DIMMs have double-sided edge connectors to maintain a small form factor with wider data widths. The trend in state-of-the-art microprocessors is also toward wider word widths. This trend is generating demand for higher performance memory components such as DIMMs.
SIMMs and DIMMS are tested for burn-in (infant mortality) and functionality. For purposes of burn-in testing, standard SIMM and DIMM sockets can be used to test for infant mortality. Functional testing is performed on automatic test equipment, typically with a "bed of nails" type interface which was originally designed to simultaneously test a plurality of individual packaged dice. However, in the case of a SIMM cards, with its single line of edge contacts on one side of the card, such test equipment may be easily adapted to electrically connect to the contacts of SIMM card placed flat in a carrier tray such as a JEDEC (Joint Electronic Device Engineering Council)-configured tray. In such a case, eight to ten of the SIMM cards may be tested, per tray, on a tester of the aforementioned configuration at one time.
The current generation of circuit card test trays for SIMMs are not, however, adaptable to handle the double-sided connectors of DIMMs because one-half of the edge connectors or contacts of the DIMM cards face opposite the test side of the tray by which contact is made. One possible solution is to design the DIMMs with through-hole or via-connected test pads extending from one side of the card to the other side, thus providing all edge connector contacts on one side of the card for test purposes. However, this potential solution requires greater use of limited circuit board real estate, as well as greater cost because of the additional traces and through-holes required. Moreover, the added conductive trace complexity may introduce more defects into the cards themselves, lowering yield for other than die-related failures.
Other circuit boards and cards employing double-sided connectors and presenting similar test and contact problems include (by way of example only) other multi-chip modules (MCMs) including other dice in addition to or in lieu of memory dice, as well as triple in-line memory modules (TRIMMs).
Electrical sockets for connecting SIMMs are taught by Lwee et al. (U.S. Pat. No. 5,256,078, Oct. 26, 1993, hereinafter the "'078" patent). Electrical sockets for connecting DIMMs are taught by Noschese et al. (U.S. Pat. No. 5,511,985, Apr. 30, 1996, hereinafter the "'985" patent). While suitable for burn-in testing, neither the '078 patent nor the '985 patent teach a circuit card receptacle for routing edge connector traces from one side of the circuit card to the other side to facilitate testing of the card from a single side. Thus, there is a need in the art for a circuit card receptacle which allows single-sided testing of circuit cards or boards having double-sided edge connectors to avoid the necessity for investing in new and different test equipment to accommodate such dual-sided connector configurations.